Proper preservation of forage is vital to both animal nutrition and performance. In the generally used AIV method, the forage pH is lowered to about 4, which inhibits microbial activity, and reduces dry matter and protein losses in the forage. The pH was earlier lowered by strong inorganic acids, but now the dominant acid used for preservation is formic acid. Strong acids are effective in inhibiting microbial growth in forage, but in the rumen this property is less advantageous. Further, if the acid does not succeed in inhibiting microbial growth completely, there is a risk that the most harmful microbial species may colonize the silage due to lack of competition.
Several salts and products of microbial or plant origin have been used for enhancing the effect of strong acids or for replacing the acids as preservatives (Bolsen, K. & Heidker, J. I., 1985, Silage Additives USA, Chalcombe Publications, UK). These additives have often been used for enhancing the growth of beneficial bacteria, such as lactic acid bacteria, and thereby for inhibiting the growth of harmful microbes, such as yeasts, molds, clostridia and coliforms. The use of lactic acid bacteria is often limited by the lack of carbohydrates suitable for the growth of these bacteria.
By-products of sugar processing, molasses, and their fermentation by-products, vinasses, are known as silage additives and additives of ruminant feed (Bolsen, K. & Heidker, J. I., 1985; Haaksma, J., 1987, The influence on growth, energy efficiency and dressing percentage, when in ratios for beef cattle containing pressed pulp soy bean meal protein was replaced by protein from vinasse or NPN, Mededeling, Instituut voor Rationele Suikerproduktie, no. 15, 23 pp.; Herold, I., Takacs, F., Beri, B. & Kota, M., 1987, Influence of chemical and biological conservation agents on silage made from green fodder with a high protein content). Due to their high nitrogen content, these products have efficiently increased the silage protein value. The molasses and vinasses, however, are not sufficiently acidic to be able to significantly lower the forage pH. Nutritionally, their high potassium content may cause problems in respect of reduced magnesium absorption (Tomas, F. M. & Potter, B. J., 1976,: The effect and site of action of potassium upon magnesium absorption in sheep, Aust. J. Agric. Res. 27, 873-880; Fontenot, J. P., Allen, V. G., Bunge, G. E. and Goff, J. P., 1989, Factors influencing magnesium absorption and metabolism in ruminants, Journal of American Science 67, 3445-3455).